Hysteresis and Oscillation in High-Efficiency Power Amplifiers

Abstract

Hysteresis in power amplifiers is investigated in detail with the aid of an efficient analysis method, compatible with commercial harmonic balance. Suppressing the input source and using, instead, an outer-tier auxiliary generator, together with the Norton equivalent of the input network, analysis difficulties associated with turning points are avoided. The turning point locus in the plane defined by any two relevant analysis parameters is obtained in a straightforward manner, using a geometrical condition. The hysteresis phenomenon is demonstrated to be due to a nonlinear resonance of the device input capacitance under near optimum matching conditions. When increasing the drain bias voltage, some points of the locus degenerate into a large-signal oscillation that cannot be detected with a stability analysis of the dc solution. In driven conditions, the oscillation will be extinguished either through synchronization or inverse Hopf bifurcations in the upper section of the multivalued curves. For an efficient stability analysis, the outer-tier method will be applied in combination with pole-zero identification and Hopf bifurcation detection. Departing from the detected oscillation, a slight variation of the input network will be carried out so as to obtain a high efficiency oscillator able to start-up from the noise level. All the tests have been carried out in a Class-E GaN PA with measured 86.8% PAE and 12.4 W output power at 0.9 GHz.

Oscillation Modes in Multiresonant Oscillator Circuits

“…In all our tests, the HB-based stability analysis [29][30] applied to doubly-autonomous quasi-periodic solutions has failed to provide any satisfactory results. This is attributed to the ill-conditioning of the conversion matrix in the presence of two Lyapunov exponents at zero [22].…”

“…In a practical oscillator, their onset from dc regime would take place for biasing conditions or element values different from the ones considered in the analysis. An example of an oscillator without a start-up from dc regime versus the analysis parameter can be found in [29].…”

“…iii) , the new solution is unstable, with two real poles on the RHS. , the new solution is unstable, with one real pole on the RHS.Applying(29) in the particular case of i(v) = av + bv 3 + dv 5 , one obtains:…”

Microwave class-E power amplifiers

“…[23] examines stability of class-E PAs, while [24] discusses effects of parameter tolerances on class-E behavior. Spatial power combining of 16 or more class-E PAs is demonstrated in [25].…”

Systematic Methodology for the Global Stability Analysis of Nonlinear Circuits

“…Only the last two methods are compatible with the use of commercial harmonic balance (HB). On the other hand, the unstable-behavior regions [4]- [5], This work was supported by the Spanish Ministry of Economy and Competitiveness and the European Regional Development Fund (ERDF/FEDER) under the research project TEC2017-88242-C3-1-R. [7], [20]- [24] in terms of relevant parameters, such as the input power, input frequency or bias voltages, can be efficiently determined through bifurcation detection. In comparison with the stability analysis, one advantage of the bifurcation analysis is that the critical poles are purely imaginary or zero at the bifurcation points, so their detection relies on standard simulation methods based on real frequencies.…”